In many contexts, the two main classes of sex steroids are androgens and estrogens, of which the most important human derivatives are testosterone and estradiol, respectively. Other contexts will include progestogens as a third class of sex steroids, distinct from androgens and estrogens. Progesterone is the most important and only naturally occurring human progestogen. In general, androgens are considered "male sex hormones", since they have masculinizing effects, while estrogens and progestogens are considered "female sex hormones"[5] although all types are present in each sex, albeit at different levels.

There are also many synthetic sex steroids. Synthetic androgens are often referred to as anabolic steroids. Synthetic estrogens and progestins are used in methods of hormonal contraception. Ethinylestradiol is a semi-synthetic estrogen. Specific compounds that have partial agonist activity for steroid receptors, and therefore act in part like natural steroid hormones, are in use in medical conditions that require treatment with steroid in one cell type, but where systemic effects of the particular steroid in the entire organism are only desirable within certain limits.[6]

1.
Estradiol
–
Estradiol, also spelled oestradiol, is a steroid, an estrogen, and the primary female sex hormone. It is named for and is important in the regulation of the estrous, while estrogen levels in men are lower compared to women, estrogens have essential functions in men as well. Estradiol is found in most vertebrates as well as crustaceans, insects, fish. Estradiol is produced especially within the follicles of the female ovaries, estradiol is biosynthesized from cholesterol through a series of chemical intermediates. One principal pathway involves the generation of 4-androstenedione, which is converted into estrone by aromatase, alternatively, 4-androstenedione can be converted into testosterone, an androgen and the primary male sex hormone, which in turn can be aromatized into estradiol. The development of sex characteristics in women is driven by estrogens, to be specific. These changes are initiated at the time of puberty, most are enhanced during the reproductive years, thus, estradiol produces breast development, and is responsible for changes in the body shape, affecting bones, joints, and fat deposition. Fat structure and skin composition are modified by estradiol and it enhances growth of the myometrium. Estradiol appears necessary to maintain oocytes in the ovary, in the luteal phase, estradiol, in conjunction with progesterone, prepares the endometrium for implantation. During pregnancy, estradiol increases due to placental production, the effect of estradiol, together with estrone and estriol, in pregnancy is less clear. They may promote blood flow, myometrial growth, stimulate breast growth and at term, promote cervical softening. In baboons, blocking of estrogen production leads to pregnancy loss, research is investigating the role of estrogens in the process of initiation of labor. Actions of estradiol are required before the exposure of progesterone in the luteal phase, the effect of estradiol upon male reproduction is complex. Estradiol is produced by action of aromatase mainly in the Leydig cells of the testis, but also by some germ cells. It functions to prevent apoptosis of male sperm cells, suppression of estradiol production in a subpopulation of subfertile men may improve the semen analysis. Males with certain sex chromosome genetic conditions, such as Klinefelters syndrome, estradiol has a profound effect on bone. Individuals without it will become tall and eunuchoid, as epiphyseal closure is delayed or may not take place, bone structure is affected also, resulting in early osteopenia and osteoporosis. Also, women past menopause experience a loss of bone mass due to a relative estrogen deficiency

2.
Estrogen
–
Estrogen or oestrogen is the primary female sex hormone as well as a medication. It is responsible for the development and regulation of the reproductive system. Estrogen may also refer to any substance, natural or synthetic, the estrane steroid estradiol is the most potent and prevalent endogenous estrogen, although several metabolites of estradiol also have estrogenic hormonal activity. They are one of three types of sex hormones, the others being androgens/anabolic steroids like testosterone and progestogens like progesterone, estrogens are synthesized in all vertebrates as well as some insects. Their presence in both vertebrates and insects suggests that sex hormones have an ancient evolutionary history. The three major naturally occurring forms of estrogen in women are estrone, estradiol, and estriol, another type of estrogen called estetrol is produced only during pregnancy. Quantitatively, estrogens circulate at lower levels than androgens in both men and women, while estrogen levels are significantly lower in males compared to females, estrogens nevertheless also have important physiological roles in males. Like all steroid hormones, estrogens readily diffuse across the cell membrane, once inside the cell, they bind to and activate estrogen receptors which in turn modulate the expression of many genes. Additionally, estrogens bind to and activate rapid-signaling membrane estrogen receptors, the three major naturally occurring estrogens in women are estrone, estradiol, and estriol. Estradiol is the predominant estrogen during reproductive years both in terms of serum levels as well as in terms of estrogenic activity. During menopause, estrone is the predominant circulating estrogen and during pregnancy estriol is the predominant circulating estrogen in terms of serum levels. Though estriol is the most plentiful of the three estrogens it is also the weakest, whereas estradiol is the strongest with a potency of approximately 80 times that of estriol. Thus, estradiol is the most important estrogen in non-pregnant females who are between the menarche and menopause stages of life, however, during pregnancy this role shifts to estriol, and in postmenopausal women estrone becomes the primary form of estrogen in the body. Another type of estrogen called estetrol is produced only during pregnancy, all of the different forms of estrogen are synthesized from androgens, specifically testosterone and androstenedione, by the enzyme aromatase. Estradiol, estrone, and estriol have all been approved as drugs and are used medically. Estetrol is currently under development for medical indications, but has not yet approved in any country. A variety of synthetic estrogen esters, such as estradiol valerate, estradiol cypionate, estradiol acetate, estradiol undecylate, polyestradiol phosphate, the aforementioned compounds behave as prodrugs to estradiol, and are longer-lasting in comparison. Esters of estrone and estriol also exist and are employed in clinical medicine, ethinylestradiol is a more potent synthetic analogue of estradiol that is used widely in hormonal contraceptives

3.
Synonym
–
A synonym is a word or phrase that means exactly or nearly the same as another word or phrase in the same language. Words that are synonyms are said to be synonymous, and the state of being a synonym is called synonymy, the word comes from Ancient Greek sýn and ónoma. An example of synonyms are the words begin, start, commence, words can be synonymous when meant in certain senses, even if they are not synonymous in all of their senses. For example, if one talks about a time or an extended time, long. Some academics call the former type cognitive synonyms to distinguish them from the latter type, some lexicographers claim that no synonyms have exactly the same meaning because etymology, orthography, phonic qualities, ambiguous meanings, usage, etc. make them unique. Different words that are similar in meaning usually differ for a reason, feline is more formal than cat, long and extended are only synonyms in one usage, synonyms are also a source of euphemisms. In the figurative sense, two words are said to be synonymous if they have the same connotation. a widespread impression that. Metonymy can sometimes be a form of synonymy, as when, for example, thus a metonym is a type of synonym, and the word metonym is a hyponym of the word synonym. The analysis of synonymy, polysemy, hyponymy, and hypernymy is inherent to taxonomy and it has applications in pedagogy and machine learning, because they rely on word-sense disambiguation and schema. Synonyms can be any part of speech, as long as both words belong to the part of speech. Such like, he expired means the same as he died, in English, many synonyms emerged in the Middle Ages, after the Norman conquest of England. While Englands new ruling class spoke Norman French, the lower classes continued to speak Old English, thus, today we have synonyms like the Norman-derived people, liberty and archer, and the Saxon-derived folk, freedom and bowman. For more examples, see the list of Germanic and Latinate equivalents in English, the purpose of a thesaurus is to offer the user a listing of similar or related words, these are often, but not always, synonyms. The word poecilonym is a synonym of the word synonym. It is not entered in most major dictionaries and is a curiosity or piece of trivia for being a word because of its meta quality as a synonym of synonym. Antonyms are words with opposite or nearly opposite meanings, for example, hot ↔ cold, large ↔ small, thick ↔ thin, synonym ↔ antonym Hypernyms and hyponyms are words that refer to, respectively, a general category and a specific instance of that category. For example, vehicle is a hypernym of car, and car is a hyponym of vehicle, homophones are words that have the same pronunciation, but different meanings. For example, witch and which are homophones in most accents, homographs are words that have the same spelling, but have different pronunciations

4.
Steroid
–
A steroid is an organic compound with four rings arranged in a specific configuration. Examples include the dietary lipid cholesterol, the sex hormones estradiol and testosterone, the steroid core structure is composed of seventeen carbon atoms, bonded in four fused rings, three six-member cyclohexane rings and one five-member cyclopentane ring. Steroids vary by the groups attached to this four-ring core. Sterols are forms of steroids with a group at position three and a skeleton derived from cholestane. They can also vary more markedly by changes to the ring structure, hundreds of steroids are found in plants, animals and fungi. All steroids are manufactured in cells from the sterols lanosterol or cycloartenol, lanosterol and cycloartenol are derived from the cyclization of the triterpene squalene. The three cyclohexane rings form the skeleton of a derivative of phenanthrene. The D ring has a cyclopentane structure, when the two methyl groups and eight carbon side chains are present, the steroid is said to have a cholestane framework. The following are some categories of steroids. In eukaryotes, steroids are found in fungi, animals, animal steroids include compounds of vertebrate and insect origin, the latter including ecdysteroids such as ecdysterone. Steroid hormones include, Sex hormones, which influence sex differences and these include androgens, estrogens, and progestagens. In popular use, the term often refers to anabolic steroids. Plant steroids include steroidal alkaloids found in Solanaceae, the phytosterols, in prokaryotes, biosynthetic pathways exist for the tetracyclic steroid framework – where its origin from eukaryotes is conjectured – and the more-common pentacyclic triterpinoid hopanoid framework. One example of how MeSH performs this classification is available at the Wikipedia MeSH catalog, examples of this classification include, The gonane is the parent 17-carbon tetracyclic hydrocarbon molecule with no alkyl sidechains. Secosteroids are a subclass of steroidal compounds resulting, biosynthetically or conceptually, major secosteroid subclasses are defined by the steroid carbon atoms where this scission has taken place. Norsteroids and homosteroids are structural subclasses of steroids formed from biosynthetic steps, the former involves enzymic ring expansion-contraction reactions, and the latter is accomplished or through ring closures of acyclic precursors with more ring atoms than the parent steroid framework. Combinations of these alterations are known in nature. Ingestion of these C-nor-D-homosteroids results in defects in lambs, cyclopia from cyclopamine

5.
Steroid hormone
–
A steroid hormone is a steroid that acts as a hormone. Steroid hormones can be grouped into two classes, corticosteroids and sex steroids, within those two classes are five types according to the receptors to which they bind, glucocorticoids, mineralocorticoids, androgens, estrogens, and progestogens. Vitamin D derivatives are a closely related hormone system with homologous receptors. They have some of the characteristics of true steroids as receptor ligands, Steroid hormones help control metabolism, inflammation, immune functions, salt and water balance, development of sexual characteristics, and the ability to withstand illness and injury. The term steroid describes both hormones produced by the body and artificially produced medications that duplicate the action for the naturally occurring steroids, the natural steroid hormones are generally synthesized from cholesterol in the gonads and adrenal glands. These forms of hormones are lipids and they can pass through the cell membrane as they are fat-soluble, and then bind to steroid hormone receptors to bring about changes within the cell. Steroid hormones are generally carried in the blood, bound to specific carrier proteins such as sex hormone-binding globulin or corticosteroid-binding globulin, further conversions and catabolism occurs in the liver, in other peripheral tissues, and in the target tissues. A variety of synthetic steroids and sterols have also been contrived, most are steroids, but some non-steroidal molecules can interact with the steroid receptors because of a similarity of shape. Some synthetic steroids are weaker or stronger than the natural steroids whose receptors they activate, some examples are sex hormone-binding globulin, corticosteroid-binding globulin, and albumin. Most studies say that hormones can affect cells when they are not bound by serum proteins. This idea is known as the free hormone hypothesis and this idea is shown in Figure 1 to the right. One study has found that these complexes are bound by megalin, a membrane receptor. The hormone then follows a pathway of action. This process is shown in Figure 2 to the right, the role of endocytosis in steroid hormone transport is not well understood and is under further investigation. In order for steroid hormones to cross the lipid bilayer of cells they must overcome barriers that would prevent their entering or exiting the membrane. Gibbs free energy is an important concept here and these hormones, which are all derived from cholesterol, have hydrophilic functional groups at either end and hydrophobic carbon backbones. These energy barriers and wells are reversed for hormones exiting membranes, Steroid hormones easily enter and exit the membrane at physiologic conditions. They have been shown experimentally to cross membranes near a rate of 20 μm/s, though it is energetically more favorable for hormones to be in the membrane than in the ECF or ICF, they do in fact leave the membrane once they have entered it

6.
Vertebrate
–
Vertebrates /ˈvɜːrtᵻbrᵻts/ comprise all species of animals within the subphylum Vertebrata /-ɑː/. Vertebrates represent the majority of the phylum Chordata, with currently about 66,000 species described. Vertebrates include the fish and the jawed vertebrates, which include the cartilaginous fish. A bony fish known as the lobe-finned fishes is included with tetrapods, which are further divided into amphibians, reptiles, mammals. Extant vertebrates range in size from the frog species Paedophryne amauensis, at as little as 7.7 mm, to the blue whale, vertebrates make up less than five percent of all described animal species, the rest are invertebrates, which lack vertebral columns. The vertebrates traditionally include the hagfish, which do not have proper vertebrae due to their loss in evolution, though their closest living relatives, hagfish do, however, possess a cranium. For this reason, the vertebrate subphylum is sometimes referred to as Craniata when discussing morphology, molecular analysis since 1992 has suggested that hagfish are most closely related to lampreys, and so also are vertebrates in a monophyletic sense. Others consider them a group of vertebrates in the common taxon of craniata. The word origin of vertebrate derives from the Latin word vertebratus, the Proto-Indo-European language origins are still unclear. Vertebrate is derived from the vertebra, which refers to any of the bones or segments of the spinal column. All vertebrates are built along the basic body plan, a stiff rod running through the length of the animal, with a hollow tube of nervous tissue above it. In all vertebrates, the mouth is found at, or right below, the remaining part of the body continuing after the anus forms a tail with vertebrae and spinal cord, but no gut. However, a few vertebrates have secondarily lost this anatomy, retaining the notochord into adulthood, such as the sturgeon, jawed vertebrates are typified by paired appendages, but this trait is not required in order for an animal to be a vertebrate. All basal vertebrates breathe with gills, the gills are carried right behind the head, bordering the posterior margins of a series of openings from the pharynx to the exterior. Each gill is supported by a cartilagenous or bony gill arch, the bony fish have three pairs of arches, cartilaginous fish have five to seven pairs, while the primitive jawless fish have seven. The vertebrate ancestor no doubt had more arches than this, as some of their relatives have more than 50 pairs of gills. In amphibians and some primitive fishes, the larvae bear external gills. These are reduced in adulthood, their function taken over by the gills proper in fishes, some amphibians retain the external larval gills in adulthood, the complex internal gill system as seen in fish apparently being irrevocably lost very early in the evolution of tetrapods

7.
Androgen
–
This includes the activity of the primary male sex organs and development of male secondary sex characteristics. Androgens were first discovered in 1936, androgens increase in both boys and girls during puberty. Androgens are also the original anabolic steroids and the precursor of all estrogens, the primary and most well-known androgen is testosterone. Dihydrotestosterone and androstenedione are less known generally, but are of importance in male development. DHT in the embryo life causes differentiation of penis, scrotum, later in life DHT contributes to balding, prostate growth and sebaceous gland activity. Although androgens are described as sex hormones, both males and females have them to varying degrees, as is also true of estrogens. They are one of three types of sex hormones, the others being estrogens like estradiol and progestogens like progesterone, the main subset of androgens, known as adrenal androgens, is composed of 19-carbon steroids synthesized in the zona reticularis, the innermost layer of the adrenal cortex. Adrenal androgens function as weak steroids, and the subset includes dehydroepiandrosterone, dehydroepiandrosterone sulfate, androstenedione, besides testosterone, other androgens include, Dehydroepiandrosterone is a steroid hormone produced in the adrenal cortex from cholesterol. It is the precursor of natural estrogens. DHEA is also called dehydroisoandrosterone or dehydroandrosterone, androstenedione is an androgenic steroid produced by the testes, adrenal cortex, and ovaries. While androstenediones are converted metabolically to testosterone and other androgens, they are also the parent structure of estrone, use of androstenedione as an athletic or bodybuilding supplement has been banned by the International Olympic Committee, as well as other sporting organizations. Androstenediol is the steroid metabolite thought to act as the regulator of gonadotropin secretion. It is found in equal amounts in the plasma and urine of both males and females. Dihydrotestosterone is a metabolite of testosterone, and a potent androgen than testosterone in that it binds more strongly to androgen receptors. It is produced in the skin and reproductive tissue, during mammalian development, the gonads are at first capable of becoming either ovaries or testes. In humans, starting at about week 4, the rudiments are present within the intermediate mesoderm adjacent to the developing kidneys. At about week 6, epithelial sex cords develop within the forming testes, in males, certain Y chromosome genes, particularly SRY, control development of the male phenotype, including conversion of the early bipotential gonad into testes. In males, the sex cords fully invade the developing gonads, the mesoderm-derived epithelial cells of the sex cords in developing testes become the Sertoli cells, which will function to support sperm cell formation

8.
Receptor (biochemistry)
–
In biochemistry and pharmacology, a receptor is a protein molecule that receives chemical signals from outside a cell. When such chemical signals bind to a receptor, they cause some form of cellular/tissue response, however, sometimes in pharmacology, the term is also used to include other proteins that are drug targets, such as enzymes, transporters and ion channels. Receptor proteins can be classified by their location, transmembrane receptors include ion channel-linked receptors, G protein-linked hormone receptors, and enzyme-linked hormone receptors. Intracellular receptors are found inside the cell, and include cytoplasmic receptors. The endogenously designated -molecule for a receptor is referred to as its endogenous ligand. E. g. the endogenous ligand for the acetylcholine receptor is acetylcholine but the receptor can also be activated by nicotine. Each receptor is linked to a specific cellular biochemical pathway, while numerous receptors are found in most cells, each receptor will only bind with ligands of a particular structure, much like how locks will only accept specifically shaped keys. When a ligand binds to its receptor, it activates or inhibits the receptors associated biochemical pathway. The ligand-binding cavities are located at the interface between the subunits, type 2, G protein-coupled receptors – This is the largest family of receptors and includes the receptors for several hormones and slow transmitters e. g. dopamine, metabotropic glutamate. They are composed of seven transmembrane alpha helices, the loops connecting the alpha helices form extracellular and intracellular domains. The aforementioned receptors are coupled to different intracellular effector systems via G proteins, the insulin receptor is an example. Type 4, Nuclear receptors – While they are called nuclear receptors, they are located in the cytoplasm. They are composed of a C-terminal ligand-binding region, a core DNA-binding domain, the core region has two zinc fingers that are responsible for recognizing the DNA sequences specific to this receptor. The N terminus interacts with other transcription factors in a ligand-independent manner. Steroid and thyroid-hormone receptors are examples of such receptors, membrane receptors may be isolated from cell membranes by complex extraction procedures using solvents, detergents, and/or affinity purification. The structures and actions of receptors may be studied by using methods such as X-ray crystallography, NMR, circular dichroism. Computer simulations of the behavior of receptors have been used to gain understanding of their mechanisms of action. Ligand binding is an equilibrium process, ligands bind to receptors and dissociate from them according to the law of mass action

9.
Nuclear receptor
–
In the field of molecular biology, nuclear receptors are a class of proteins found within cells that are responsible for sensing steroid and thyroid hormones and certain other molecules. In response, these work with other proteins to regulate the expression of specific genes, thereby controlling the development, homeostasis. Nuclear receptors have the ability to bind to DNA and regulate the expression of adjacent genes. The regulation of expression by nuclear receptors generally only happens when a ligand — a molecule that affects the receptors behavior — is present. A unique property of nuclear receptors that differentiates them from classes of receptors is their ability to directly interact with. As a consequence, nuclear receptors play key roles in embryonic development and adult homeostasis. As discussed below, nuclear receptors may be classified according to either mechanism or homology, Nuclear receptors are specific to metazoans and are not found in protists, algae, fungi, or plants. There are 270 nuclear receptors in the nematode C. elegans alone, humans, mice, and rats have respectively 48,49, and 47 nuclear receptors each. Ligands that bind to and activate nuclear receptors include lipophilic substances such as hormones, vitamins A and D. Because the expression of a number of genes is regulated by nuclear receptors. A number of receptors, referred to as orphan receptors, have no known endogenous ligands. Some of these such as FXR, LXR, and PPAR bind a number of metabolic intermediates such as fatty acids. These receptors hence may function as metabolic sensors, other nuclear receptors, such as CAR and PXR appear to function as xenobiotic sensors up-regulating the expression of cytochrome P450 enzymes that metabolize these xenobiotics. Most nuclear receptors have molecular masses between 50,000 and 100,000 daltons, Nuclear receptors are modular in structure and contain the following domains, N-terminal regulatory domain, Contains the activation function 1 whose action is independent of the presence of ligand. The transcriptional activation of AF-1 is normally very weak, but it does synergize with AF-2 in the E-domain to produce a more robust upregulation of gene expression, the A-B domain is highly variable in sequence between various nuclear receptors. DNA-binding domain, Highly conserved domain containing two zinc fingers that binds to sequences of DNA called hormone response elements. Hinge region, Thought to be a domain that connects the DBD with the LBD. Influences intracellular trafficking and subcellular distribution, ligand binding domain, Moderately conserved in sequence and highly conserved in structure between the various nuclear receptors

10.
Signaling cascade
–
Proteins responsible for detecting stimuli are generally termed receptors, although in some cases the term sensor is used. The changes elicited by ligand binding in a receptor give rise to a cascade of events along a signalling pathway. When signalling pathways interact with one another they form networks, which allow cellular responses to be coordinated and these molecular events are the basic mechanisms controlling cell growth, proliferation, metabolism and many other processes. In multicellular organisms, signal transduction pathways have evolved to regulate cell communication in a variety of ways. Each component of a pathway is classified according to the role it plays with respect to the initial stimulus. Ligands are termed first messengers, while receptors are the signal transducers, such effectors are often linked to second messengers, which can activate secondary effectors, and so on. Depending on the efficiency of the nodes, a signal can be amplified, as with other signals, the transduction of biological signals is characterised by delay, noise and interference, which can range from negligible to pathological. With the advent of computational biology, the analysis of signalling pathways and networks has become a tool to understand cellular functions. The basis for signal transduction is the transformation of a certain stimulus into a biochemical signal, traditionally, signals that reach the central nervous system are classified as senses. These are transmitted from neuron to neuron in a process called synaptic transmission, many other intercellular signal relay mechanisms exist in multicellular organisms, such as those that govern embryonic development. The majority of signal transduction pathways involve the binding of signalling molecules, known as ligands, the combination of a signaling molecule with a receptor causes a change in the conformation of the receptor, known as receptor activation. Most ligands are soluble molecules from the medium which bind to cell surface receptors. These include growth factors, cytokines and neurotransmitters, components of the extracellular matrix such as fibronectin and hyaluronan can also bind to such receptors. In addition, some such as steroid hormones are lipid-soluble. In the case of hormone receptors, their stimulation leads to binding to the promoter region of steroid-responsive genes. Not all classifications of signalling molecules take into account the nature of each class member. For example, odorants belong to a range of molecular classes, as do neurotransmitters. Moreover, some molecules may fit more than one class, e. g. epinephrine is a neurotransmitter when secreted by the central nervous system

11.
Peptide
–
Peptides are biologically occurring short chains of amino acid monomers linked by peptide bonds. The covalent chemical bonds are formed when the group of one amino acid reacts with the amine group of another. The shortest peptides are dipeptides, consisting of 2 amino acids joined by a peptide bond, followed by tripeptides, tetrapeptides. A polypeptide is a long, continuous, and unbranched peptide chain, hence, peptides fall under the broad chemical classes of biological oligomers and polymers, alongside nucleic acids, oligosaccharides and polysaccharides, etc. Peptides are distinguished from proteins on the basis of size, all peptides except cyclic peptides have an N-terminal and C-terminal residue at the end of the peptide. Ribosomal peptides Ribosomal peptides are synthesized by translation of mRNA and they are often subjected to proteolysis to generate the mature form. These function, typically in higher organisms, as hormones and signaling molecules, some organisms produce peptides as antibiotics, such as microcins. Since they are translated, the amino acid residues involved are restricted to those utilized by the ribosome, however, these peptides frequently have posttranslational modifications such as phosphorylation, hydroxylation, sulfonation, palmitoylation, glycosylation and disulfide formation. In general, they are linear, although lariat structures have been observed, more exotic manipulations do occur, such as racemization of L-amino acids to D-amino acids in platypus venom. Nonribosomal peptides Nonribosomal peptides are assembled by enzymes that are specific to each peptide, the most common non-ribosomal peptide is glutathione, which is a component of the antioxidant defenses of most aerobic organisms. Other nonribosomal peptides are most common in organisms, plants. These complexes are often out in a similar fashion. These peptides are often cyclic and can have highly complex cyclic structures, since the system is closely related to the machinery for building fatty acids and polyketides, hybrid compounds are often found. The presence of oxazoles or thiazoles often indicates that the compound was synthesized in this fashion, Peptones See also Tryptone Peptones are derived from animal milk or meat digested by proteolysis. In addition to containing small peptides, the material includes fats, metals, salts, vitamins. Peptones are used in nutrient media for growing bacteria and fungi, Peptide fragments Peptide fragments refer to fragments of proteins that are used to identify or quantify the source protein. Peptides received prominence in molecular biology for several reasons, the first is that peptides allow the creation of peptide antibodies in animals without the need of purifying the protein of interest. This involves synthesizing antigenic peptides of sections of the protein of interest and these will then be used to make antibodies in a rabbit or mouse against the protein

12.
Luteinizing hormone
–
Luteinizing hormone is a hormone produced by gonadotropic cells in the anterior pituitary gland. In females, a rise of LH triggers ovulation and development of the corpus luteum. In males, where LH had also been called interstitial cell–stimulating hormone, each monomeric unit is a glycoprotein molecule, one alpha and one beta subunit make the full, functional protein. Its structure is similar to that of the other glycoprotein hormones, follicle-stimulating hormone, thyroid-stimulating hormone, LH has a beta subunit of 120 amino acids that confers its specific biologic action and is responsible for the specificity of the interaction with the LH receptor. This beta subunit contains an amino acid sequence that exhibits large homologies with that of the subunit of hCG. However, the hCG beta subunit contains an additional 24 amino acids, the different composition of these oligosaccharides affects bioactivity and speed of degradation. The biologic half-life of LH is 20 minutes, shorter than that of FSH, the gene for the alpha subunit is located on chromosome 6q12.21. The luteinizing hormone beta subunit gene is localized in the LHB/CGB gene cluster on chromosome 19q13.32, in contrast to the alpha gene activity, beta LH subunit gene activity is restricted to the pituitary gonadotropic cells. It is regulated by the hormone from the hypothalamus. Inhibin, activin, and sex hormones do not affect genetic activity for the beta subunit production of LH, in females, ovulation, maintaining of corpus luteum and secretion of progesterone. LH supports theca cells in the ovaries that provide androgens and hormonal precursors for estradiol production, at the time of menstruation, FSH initiates follicular growth, specifically affecting granulosa cells. With the rise in estrogens, LH receptors are expressed on the maturing follicle. However another theory of the LH peak is a feedback mechanism from estradiol. The levels keep rising through the phase and when they reach an unknown threshold. This effect is opposite from the negative feedback mechanism presented at lower levels. In other words, the mechanism are not yet clear, the increase in LH production only lasts for 24 to 48 hours. LH is necessary to maintain luteal function for the two weeks of the menstrual cycle. If pregnancy occurs, LH levels will decrease, and luteal function will instead be maintained by the action of hCG, LH acts upon the Leydig cells of the testis and is regulated by gonadotropin-releasing hormone

13.
Follicle-stimulating hormone
–
Follicle-stimulating hormone is a gonadotropin, a glycoprotein polypeptide hormone. FSH is synthesized and secreted by the cells of the anterior pituitary gland, and regulates the development, growth, pubertal maturation. FSH and luteinizing hormone work together in the reproductive system, FSH is a 35.5 kDa glycoprotein heterodimer, consisting of two polypeptide units, alpha and beta. Its structure is similar to those of luteinizing hormone, thyroid-stimulating hormone, the alpha subunits of the glycoproteins LH, FSH, TSH, and hCG are identical and consist of about 96 amino acids, while the beta subunits vary. Both subunits are required for biological activity, FSH has a beta subunit of 111 amino acids, which confers its specific biologic action, and is responsible for interaction with the follicle-stimulating hormone receptor. The sugar portion of the hormone is covalently bonded to asparagine, and is composed of N-acetylgalactosamine, mannose, N-acetylglucosamine, galactose, in humans, the gene for the alpha subunit is located at cytogenetic location 6q14.3. It is expressed in two types, most notably the basophils of the anterior pituitary. The gene for the FSH beta subunit is located on chromosome 11p13, and is expressed in gonadotropes of the cells, controlled by GnRH, inhibited by inhibin. FSH regulates the development, growth, pubertal maturation and reproductive processes of the human body, in both males and females, FSH stimulates the maturation of germ cells. In males, FSH induces Sertoli cells to secrete androgen-binding proteins, in females, FSH initiates follicular growth, specifically affecting granulosa cells. With the concomitant rise in inhibin B, FSH levels then decline in the follicular phase. This seems to be critical in selecting only the most advanced follicle to proceed to ovulation, at the end of the luteal phase, there is a slight rise in FSH that seems to be of importance to start the next ovulatory cycle. Control of FSH release from the gland is unknown. Low frequency gonadotropin-releasing hormone pulses increase FSH mRNA levels in the rat, GnRH has been shown to play an important role in the secretion of FSH, with hypothalamic-pituitary disconnection leading to a cessation of FSH. GnRH administration leads to a return of FSH secretion, FSH is subject to oestrogen feed-back from the gonads via the hypothalamic pituitary gonadal axis. FSH stimulates the growth and recruitment of immature ovarian follicles in the ovary, in early antral follicles, FSH is the major survival factor that rescues the small antral follicles from apoptosis. In the luteal-follicle phase transition period the serum levels of progesterone and estrogen decrease and no longer suppress the release of FSH, the cohort of small antral follicles is normally sufficiently in number to produce enough Inhibin B to lower FSH serum levels. When the follicle matures and reaches 8–10 mm in diameter it starts to secrete significant amounts of estradiol, normally in humans only one follicle becomes dominant and survives to grow to 18–30 mm in size and ovulate, the remaining follicles in the cohort undergo atresia

14.
Testes
–
The testicle or testis is the male gonad in animals. Like the ovaries to which they are homologous, the testicles are components of both the system and the endocrine system. The primary functions of the testes are to produce sperm and to produce androgens, both functions of the testicle are influenced by gonadotropic hormones produced by the anterior pituitary. Luteinizing hormone results in testosterone release, the presence of both testosterone and follicle-stimulating hormone is needed to support spermatogenesis. Almost all healthy male vertebrates have two testicles and they are typically of similar size, although in sharks, that on the right side is usually larger, and in many bird and mammal species, the left may be the larger. The primitive jawless fish have only a single testis, located in the midline of the body, the testicles of a dromedary camel are 7–10 cm long,4.5 cm deep and 5 cm in width. The right testicle is often smaller than the left, the testicles of a male red fox attain their greatest weight in December–February. Spermatogenesis in male golden jackals occurs 10–12 days before the females enter estrus and, during this time, in mammals, the testes are often contained within an extension of the abdomen called the scrotum. In mammals with external testes it is most common for one testicle to hang lower than the other. While the size of the varies, it is estimated that 21. 9% of men have their higher testicle being their left. This is due to differences in the anatomical structure on the right. In healthy European adult humans, average volume is 18 cm³ per testis. The average testicle size after puberty measures up to around 2 inches long,0.8 inches in breadth, measurement in the living adult is done in two basic ways, comparing the testicle with ellipsoids of known sizes. Measuring the length, depth and width with a ruler, a pair of calipers or ultrasound imaging, the volume is then calculated using the formula for the volume of an ellipsoid, 4/3 π × × ×. Human testicles are smaller than chimpanzee testicles but larger than gorilla testicles, under a tough membranous shell, the tunica albuginea, the testis of amniotes and some teleost fish, contains very fine coiled tubes called seminiferous tubules. The tubules are lined with a layer of cells that from puberty into old age, the sperm move into the vas deferens, and are eventually expelled through the urethra and out of the urethral orifice through muscular contractions. Amphibians and most fish do not possess seminiferous tubules, instead, the sperm are produced in spherical structures called sperm ampullae. These are seasonal structures, releasing their contents during the breeding season, before the next breeding season, new sperm ampullae begin to form and ripen

15.
Testosterone
–
Testosterone is the primary male sex hormone and an anabolic steroid. In addition, testosterone is essential for health and well-being, insufficient levels of testosterone in men may lead to abnormalities including frailty and bone loss. Testosterone is also used as a medication to treat male hypogonadism, since testosterone levels gradually decrease as men age, synthetic testosterone is sometimes prescribed to older men to counteract this deficiency. Testosterone is a steroid from the class containing a keto. It is biosynthesized in several steps from cholesterol and is converted in the liver to inactive metabolites and it exerts its action through binding to and activation of the androgen receptor. In humans and most other vertebrates, testosterone is secreted primarily by the testicles of males and, to a lesser extent, small amounts are also secreted by the adrenal glands. On average, in males, levels of testosterone are about 7–8 times as great as in adult females. As the metabolic consumption of testosterone in males is greater, the production is about 20 times greater in men. Females are also sensitive to the hormone. In general, androgens such as testosterone promote protein synthesis and thus growth of tissues with androgen receptors, Testosterone can be described as having virilising and anabolic effects. Anabolic effects include growth of mass and strength, increased bone density and strength. Many of these fall into the category of secondary sex characteristics. Testosterone effects can also be classified by the age of usual occurrence, for postnatal effects in both males and females, these are mostly dependent on the levels and duration of circulating free testosterone. Effects before birth are divided into two categories, classified in relation to the stages of development, the first period occurs between 4 and 6 weeks of the gestation. There is also development of the gland and seminal vesicles. During the second trimester, androgen level is associated with gender formation and this period affects the femininization or masculinization of the fetus and can be a better predictor of feminine or masculine behaviours such as sex typed behaviour than an adults own levels. Early infancy androgen effects are the least understood, in the first weeks of life for male infants, testosterone levels rise. The levels remain in a range for a few months

16.
Progestogen
–
Progestogens, also sometimes spelled progestagens or gestagens, are a class of steroid hormones that bind to and activate the progesterone receptor. Progesterone is the major and most important progestogen in the body, major examples of progestins include the 17α-hydroxyprogesterone derivative medroxyprogesterone acetate and the 19-nortestosterone derivative norethisterone. The progestogens are named for their function in maintaining pregnancy, although they are present at other phases of the estrous. They are one of three types of sex hormones, the others being estrogens like estradiol and androgens/anabolic steroids like testosterone. The progestogens are one of the five classes of steroid hormones, in addition to the androgens, estrogens, glucocorticoids. All endogenous progestogens are characterized by their basic 21-carbon skeleton, called a pregnane skeleton, in similar manner, the estrogens possess an estrane skeleton, and androgens, an androstane skeleton. The terms progesterone, progestogen, and progestin are mistakenly used interchangeably both in the literature and in clinical settings. While the progestins are structural analogues of progesterone, they are not functional analogues, the most important progestogen in the body is progesterone. Other endogenous progestogens include 16α-hydroxyprogesterone, 17α-hydroxyprogesterone, 20α-dihydroprogesterone, 5α-dihydroprogesterone, 11-deoxycorticosterone, progesterone is produced from cholesterol with pregnenolone as a metabolic intermediate. In the first step in the pathway, cholesterol is converted into pregnenolone]]. Thus, many tissues producing steroids, including the adrenal glands, testes, in some tissues, the enzymes required for the final product are not all located in a single cell. For example, in ovarian follicles, cholesterol is converted to androstenedione, an androgen, in the theca cells, fetal adrenal glands also produce pregnenolone in some species, which is converted into progesterone and estrogens by the placenta. In the human, the fetal adrenals produce dehydroepiandrosterone via the pregnenolone pathway, progesterone is the major progestogen produced by the corpus luteum of the ovary in all mammalian species. Luteal cells possess the enzymes to convert cholesterol to pregnenolone. Progesterone is highest in the phase of the estrous cycle. The role of the placenta in progestogen production varies by species, in the sheep, horse, and human, the placenta takes over the majority of progestogen production, whereas in other species the corpus luteum remains the primary source of progestogens. In the sheep and human, progesterone is the major placental progestogen, the equine placenta produces a variety of progestogens, primarily 5α-dihydroprogesterone and 5α, 20α-tetrahydroprogesterone, beginning on day 60. A complete luteo-placental shift occurs by day 120–150, comparison of progestogens List of steroidal progestogens List of progestogens available in the United States Utian WH, Shoupe D, Bachmann G, Pinkerton JV, Pickar JH

17.
Androstenediol
–
Δ5-Diol is a direct metabolite of the most abundant steroid produced by the human adrenal cortex, DHEA. It is less androgenic than the compound, Δ4-androstenediol, and has been found to stimulate the immune system. When administered to rats, Δ5-diol, in vivo, has approximately 1. 4% of the androgenicity of DHEA,0. 54% of the androgenicity of androstenedione, Δ5-Diol possesses potent estrogenic activity, similarly to DHEA and 3β-androstanediol. It has approximately 6% and 17% of the affinity of estradiol at the ERα and ERβ, the value of Δ5-diol as a radiation countermeasure is based mainly on its stimulation of production of white blood cells and platelets. The clinical trials with rhesus monkeys was successful, according to the Hollis-Eden report, only 12. 5% of the 40 Neumune-treated animals died versus 32. 5% in the placebo group. Hollis-Eden had applied for a contract from the U. S. Government under the BioShield Request for Proposals for radiation countermeasures, after being encouraged for 2.5 years that Neumune was in the competitive range, on March 9,2007, the RFP was canceled by HHS. According to HHS, the product was no longer in the competitive range, as a result, Hollis-Eden has now withdrawn from the radiation countermeasure field. 3α-Androstanediol 3β-Androstanediol Regenerative Medicine - Official Hollis-Eden Pharmaceuticals website New Scientist article on AED as an anti-radiation sickness drug

18.
Androstenedione
–
In turn, Δ4-dione is also a precursor of dihydrotestosterone, estrogens such as estradiol and estrone, and the neurosteroid 3α-androstanediol. Δ4-Dione is the precursor of the androgen and estrogen sex hormones. Δ4-Dione can be biosynthesized in one of two ways, the primary pathway involves conversion of 17α-hydroxypregnenolone to DHEA by way of 17, 20-lyase, with subsequent conversion of DHEA to Δ4-dione via the enzyme 3β-hydroxysteroid dehydrogenase. The secondary pathway involves conversion of 17α-hydroxyprogesterone, most often a precursor to cortisol, to directly by way of 17. Thus,17, 20-lyase is required for the synthesis of Δ4-dione, Δ4-Dione is produced in the adrenal glands and the gonads. The production of adrenal Δ4-dione is governed by adrenocorticotrophic hormone, whereas production of gonadal Δ4-dione is under control by the gonadotropins, in premenopausal women, the adrenal glands and ovaries each produce about half of the total Δ4-dione. After menopause, Δ4-dione production is about halved, due primarily to the reduction of the steroid secreted by the ovary, nevertheless, Δ4-dione is the principal steroid produced by the postmenopausal ovary. Some Δ4-dione is also secreted into the plasma, and may be converted in peripheral tissues to testosterone, Δ4-Dione is converted to either testosterone or estrogen. In males, conversion of Δ4-dione to testosterone requires the enzyme 17β-hydroxysteroid dehydrogenase, in females, Δ4-dione is released into the blood by theca cells. Conversion of Δ4-dione to estrogen requires the enzyme aromatase, Δ4-Dione is a substrate for estrogen production in granulosa cells which produce aromatase. Thus, theca cells and granulosa cells work together to form estrogens, levels are normally 30-200 ng/dL in females and 40-150 ng/dL in males. Androstanedione is a 5α-reduced metabolite of 4-androstenedione which serves as an intermediate in the biosynthesis of the androgen, Δ4-Dione has been found to possess estrogenic actions, similarly to other DHEA metabolites. However, in contrast to 5-androstenediol, its affinity for the receptors is very low. In juveniles aged 6-8 years old, there is a rise in androstenedione secretion along with DHEA called adrenarche and this rise in androstenedione and DHEA is hypothesized to play a crucial role for learning social, cultural and ecological skills, such as the development and understanding of sexual attraction. Δ4-Dione was manufactured as a supplement, often called andro for short. Sports Illustrated credits Patrick Arnold for introducing Δ4-dione to the North American market, Andro was legal and able to be purchased over the counter, and, as a consequence, it was in common use in Major League Baseball throughout the 1990s by record-breaking sluggers like Mark McGwire. The supplement is banned by the World Anti-Doping Agency, and from the Olympic Games, the International Olympic Committee in 1997 banned Δ4-dione and placed it under the category of androgenic-anabolic steroids. Δ4-Dione is banned by MLB, the NFL, USOC, NCA, barry R. McCaffrey, the director of the White Houses Office of National Drug Control Policy, attempted to determine whether Δ4-dione could be classified as an anabolic steroid in July 1999

19.
Dehydroepiandrosterone
–
Dehydroepiandrosterone, also known as androstenolone, is an endogenous steroid hormone. However, DHEA also has a variety of biological effects in its own right, binding to an array of nuclear and cell surface receptors. Exogenous dehydroepiandrosterone used as a medication is often called prasterone, in women with adrenal insufficiency and the healthy elderly there is insufficient evidence to support the use of DHEA. DHEA is sometimes used as an androgen in hormone replacement therapy for menopause, a long-lasting ester prodrug of DHEA, prasterone enanthate, is used in combination with estradiol valerate for this indication. DHEA is produced naturally in the body, but the long-term effects of its use are largely unknown. In the short term, several studies have noted few adverse effects, in a study by Chang et al. DHEA was administered at a dose of 200 mg/day for 24 weeks with slight androgenic effects noted, another study utilized a dose up to 400 mg/day for 8 weeks with few adverse events reported. A longer term study followed patients dosed with 50 mg of DHEA for 12 months with the number, another study delivered a dose of 50 mg of DHEA for 10 months with no serious adverse events reported. As a hormone precursor, there has been a smattering of reports of side effects caused by the hormone metabolites of DHEA. It is not known whether DHEA is safe for long-term use, some researchers believe DHEA supplements might actually raise the risk of breast cancer, prostate cancer, heart disease, diabetes, and stroke. DHEA may stimulate tumor growth in types of cancer that are sensitive to hormones, such as types of breast, uterine. DHEA may increase prostate swelling in men with benign prostatic hyperplasia, high doses may cause aggressiveness, irritability, trouble sleeping, and the growth of body or facial hair on women. It also may stop menstruation and lower the levels of HDL, other reported side effects include acne, heart rhythm problems, liver problems, hair loss, and oily skin. It may also alter the bodys regulation of blood sugar, patients on hormone replacement therapy may have more estrogen-related side effects when taking DHEA. This supplement may also interfere with other medicines, and potential interactions between it and drugs and herbs are possible, DHEA is produced from cholesterol through two cytochrome P450 enzymes. Cholesterol is converted to pregnenolone by the enzyme P450 scc, then another enzyme, CYP17A1, converts pregnenolone to 17α-hydroxypregnenolone, regular exercise is known to increase DHEA production in the body. Calorie restriction has also shown to increase DHEA in primates. Some theorize that the increase in endogenous DHEA brought about by calorie restriction is partially responsible for the life expectancy known to be associated with calorie restriction

20.
Dihydrotestosterone
–
Dihydrotestosterone, or 5α-dihydrotestosterone, also known as 5α-androstan-17β-ol-3-one, is an endogenous androgen sex steroid and hormone. The enzyme 5α-reductase catalyzes the formation of DHT from testosterone in certain tissues including the prostate gland, seminal vesicles, epididymides, skin, hair follicles, liver and this enzyme mediates reduction of the C4-5 double bond of testosterone. Relative to testosterone, DHT is considerably more potent as an agonist of the androgen receptor. DHT has an affinity of 0.25 to 0.5 nM for the human AR, the dissociation rate of DHT from the AR is 5-fold slower than that of testosterone. The EC50 of DHT for activation of the AR is 0.13 nM, in bioassays, DHT has been found to be 2. 5- to 10-fold more potent than testosterone. The terminal half-life of DHT in the body is longer than that of testosterone, a study of transdermal DHT and testosterone treatment reported terminal half-lives of 2.83 hours and 1.29 hours, respectively. An example illustrating the significance of DHT for the development of sex characteristics is congenital 5α-reductase type II deficiency. This genetic mutation can result in pseudohermaphroditism, the condition typically presents with underdeveloped male genitalia and prostate. Males with this condition are often raised as girls due to their lack of male genitalia. At the onset of puberty, although their DHT levels remain very low and their musculature develops like that of other male adults. After puberty, men with this condition have a deficiency of pubic and body hair. They also reportedly have no incidence of prostate cancer, unlike other androgens such as testosterone, DHT cannot be converted by the enzyme aromatase into an estrogen like estradiol. In the case of female androgenic alopecia, on the hand, the situation is more complex. Women with increased levels of DHT may develop symptoms of such as certain androgynous masculine secondary sex characteristics, including a deepened voice. In men, prostate growth and differentiation are highly dependent on androgens, especially DHT, both finasteride and dutasteride are approved for the treatment of BPH and androgenic alopecia. Dutasteride is three times more potent than finasteride in inhibiting the type II enzyme and 100 times more potent than finasteride in inhibiting the type I form of the DHT-producing enzyme, both finasteride and dutasteride are potent inhibitors of the third isotype of the enzyme. Acne, hirsutism, and seborrhea are also DHT-related conditions, in addition, antiandrogens like cyproterone acetate, spironolactone, and bicalutamide, as well as estrogens like ethinylestradiol, may also be used to treat these conditions. DHT is synthesized from testosterone by the enzyme 5α-reductase, in males, approximately 5% of testosterone undergoes 5α-reduction into DHT

21.
Estetrol
–
Estetrol, or 15α-hydroxyestriol, is an estrogen steroid hormone, found in detectable levels in maternal serum at around week 9 of pregnancy. Estetrol is a steroid, produced by the fetal liver during pregnancy only. This natural hormone was discovered in urine of pregnant women by Diczfalusy, estetrol has the structure of an estrogenic steroid with four hydroxyl groups which explains the acronym E4. Estetrol is synthesized in the liver from estradiol and estriol by the two enzymes 15α- and 16α-hydroxylase. Alternatively, estetrol is synthesized with 15α-hydroxylation of 16α-hydroxy-DHEA sulfate as an intermediate step, after birth the neonatal liver rapidly loses its capacity to synthesize E4 because these two enzymes are no longer expressed. Estetrol reaches the circulation through the placenta and was already detected at nine weeks of pregnancy in maternal urine. During the second trimester of pregnancy high levels were found in maternal plasma, so far the physiological function of E4 is unknown. The possible use of E4 as a marker for fetal well-being has been studied quite extensively, however, due to the large intra- and inter-individual variation of maternal E4 plasma levels during pregnancy this appeared not to be feasible. Since 2001, E4 has been studied extensively, high oral absorption and bioavailability with a 2–3 hours elimination half-life in the rat has been established. In the human E4 showed a high and dose-proportional oral bioavailability, results from in vitro studies showed that E4 binds highly selective to the estrogen receptors with preference for the ERα form of the receptor unlike ethinylestradiol and 17β-estradiol. Also in contrast with EE and especially with E2, E4 does not bind to sex hormone binding globulin, the properties of E4 have also been investigated in a series of highly predictive, well validated pharmacological in vivo rat models. In these models, E4 exhibited estrogenic effects on the vagina, all these effects of E4 were dose-dependent with maximal effects at comparable dose levels. Surprisingly, E4 prevented tumour development in a DMBA mammary tumour model to an extent and at a level similar to the anti-estrogen tamoxifen. This anti-estrogenic effect of E4 in the presence of E2 has also observed in in vitro studies using human breast cancer cells. The data indicate that E4 may be suitable for use in several indications e. g. contraception, hormone replacement therapy, breast cancer, prostate cancer, estetrol is being developed as estrogenic component in the oral contraceptive pill and for hormone replacement therapy by Mithra Pharmaceuticals. Pantarhei Oncology B. V. is developing estetrol for the treatment of breast cancer and prostate cancer

22.
Estrone
–
Estrone, or oestrone, also known as estra-1,3, 5-trien-3-ol-17-one, is an estrogenic hormone secreted by the ovary as well as adipose tissue. It is one of natural estrogens, which also include estriol and estradiol. Estrone is the least abundant of the three hormones, estradiol is present almost always in the female body, and estriol is abundant primarily during pregnancy. Estrone was discovered and isolated by German chemist Adolf Butenandt and it was formerly marketed under the brand name Theelin in the United States for intramuscular injection, but this formulation is no longer available. Estrone is synthesized via aromatase from 4-androstenedione, the conversion consists of the demethylation of the C19 position and the aromatization of the A ring. This reaction is similar to the conversion of testosterone to estradiol via aromatase, estrone is also reversibly produced from estradiol via 17β-hydroxysteroid dehydrogenase. Estrone has the chemical name 3-hydroxyestra-1,3, 5-triene-17-one or estra-1,3, 5-triene-3-ol-17-one and it is an odorless, solid crystalline powder, white in color with a melting point of 254.5 °C and a specific gravity of 1.23. At high temperatures estrone is combustible and the products of combusting estrone are carbon monoxide and carbon dioxide. Estrone is known to be a carcinogen for human females as well as a cause of breast tenderness or pain, nausea, headache, hypertension, in men, estrone has been known to cause anorexia, nausea, vomiting, and erectile dysfunction. Estrone is relevant to health and disease states because of its conversion to estrone sulfate, estrone sulfate acts as a reservoir that can be converted as needed to the more active estradiol. It is the predominant estrogen in postmenopausal women, the use of estrone in norsteroid, a derivative of steroids, and in medications can cause its release into the environment through waste streams. Estrone has been proven to be a carcinogen for human females. The Occupational Safety and Health Administration classifies estrone as an OSHA Select carcinogen, mothers lactating can also experience a decrease in the production of breast milk. Estrone can be found in the urine of pregnant women and can also be excreted in feces, estrone is commonly produced in large quantities of the livers of transgender women who take oral estradiol. This is a result of first pass metabolism converting estradiol to estrone, exposure to estrone can cause anorexia, nausea, vomiting, edema, feminization including gynecomastia and erectile dysfunction in men. If exposure of estrone to the eyes occurs, contacts should be removed and rinsed with water for 15 minutes, if any irritation occurs medical attention may be necessary. Exposure of estrone to the eyes can be prevented through the use of safety goggles, if exposure of estrone to the skin occurs, the effected area should be washed with soap and water and then covered with an emollient or moisturizer. Medical attention may be necessary if irritation persists, exposure of estrone can be prevented through the use protective gloves, the wearing of pants, shirts that cover the entire upper body, and lab coat

23.
Anabolic steroid
–
They are anabolic and increase protein within cells, especially in skeletal muscles. The word anabolic, referring to anabolism, comes from the Greek ἀναβολή anabole and they are one of three types of sex hormone agonists, the others being estrogens like estradiol and progestogens like progesterone. Health risks can be produced by long-term use or excessive doses of AAS and these effects include harmful changes in cholesterol levels, acne, high blood pressure, liver damage, and dangerous changes in the structure of the left ventricle of the heart. Conditions pertaining to hormonal imbalances such as gynecomastia and testicular size reduction may also be caused by AAS and their use is referred to as doping and banned by most major sporting bodies. For many years, AAS have been by far the most detected doping substances in IOC-accredited laboratories, in countries where AAS are controlled substances, there is often a black market in which smuggled, clandestinely manufactured or even counterfeit drugs are sold to users. AAS have largely replaced in this setting by synthetic protein hormones that selectively stimulate growth of blood cell precursors. Growth stimulation, AAS can be used by pediatric endocrinologists to treat children with growth failure, however, the availability of synthetic growth hormone, which has fewer side effects, makes this a secondary treatment. Stimulation of appetite and preservation and increase of mass, AAS have been given to people with chronic wasting conditions such as cancer. Induction of male puberty, Androgens are given to many boys distressed about extreme delay of puberty, Testosterone is now nearly the only androgen used for this purpose and has been shown to increase height, weight, and fat-free mass in boys with delayed puberty. Male contraception, in the form of testosterone enanthate, potential for use in the near-future as a safe, reliable, stimulation of lean body mass and prevention of bone loss in elderly men, as some studies indicate. Hormone replacement for men with low levels of testosterone, also effective in improving libido for elderly males, most steroid users are not athletes. Between 1 million and 3 million people are thought to have misused AAS in the United States, another study found that non-medical use of AAS among college students was at or less than 1%. According to a recent survey,78, the same study found that individuals using AAS for non-medical purposes had a higher employment rate and a higher household income than the general population. AAS users tend to be disillusioned by the portrayal of AAS as deadly in the media, according to one study, AAS users also distrust their physicians and in the sample 56% had not disclosed their AAS use to their physicians. A recent study has shown that long term AAS users were more likely to have symptoms of muscle dysmorphia. A recent study in the Journal of Health Psychology showed that many believed that steroids used in moderation were safe. AAS have been used by men and women in different kinds of professional sports to attain a competitive edge or to assist in recovery from injury. These sports include bodybuilding, weightlifting, shot put and other track and field, cycling, baseball, wrestling, mixed martial arts, boxing, football, such use is prohibited by the rules of the governing bodies of most sports

24.
PubMed Identifier
–
PubMed is a free search engine accessing primarily the MEDLINE database of references and abstracts on life sciences and biomedical topics. The United States National Library of Medicine at the National Institutes of Health maintains the database as part of the Entrez system of information retrieval, from 1971 to 1997, MEDLINE online access to the MEDLARS Online computerized database primarily had been through institutional facilities, such as university libraries. PubMed, first released in January 1996, ushered in the era of private, free, home-, the PubMed system was offered free to the public in June 1997, when MEDLINE searches via the Web were demonstrated, in a ceremony, by Vice President Al Gore. Information about the journals indexed in MEDLINE, and available through PubMed, is found in the NLM Catalog. As of 5 January 2017, PubMed has more than 26.8 million records going back to 1966, selectively to the year 1865, and very selectively to 1809, about 500,000 new records are added each year. As of the date,13.1 million of PubMeds records are listed with their abstracts. In 2016, NLM changed the system so that publishers will be able to directly correct typos. Simple searches on PubMed can be carried out by entering key aspects of a subject into PubMeds search window, when a journal article is indexed, numerous article parameters are extracted and stored as structured information. Such parameters are, Article Type, Secondary identifiers, Language, publication type parameter enables many special features. As these clinical girish can generate small sets of robust studies with considerable precision, since July 2005, the MEDLINE article indexing process extracts important identifiers from the article abstract and puts those in a field called Secondary Identifier. The secondary identifier field is to store numbers to various databases of molecular sequence data, gene expression or chemical compounds. For clinical trials, PubMed extracts trial IDs for the two largest trial registries, ClinicalTrials. gov and the International Standard Randomized Controlled Trial Number Register, a reference which is judged particularly relevant can be marked and related articles can be identified. If relevant, several studies can be selected and related articles to all of them can be generated using the Find related data option, the related articles are then listed in order of relatedness. To create these lists of related articles, PubMed compares words from the title and abstract of each citation, as well as the MeSH headings assigned, using a powerful word-weighted algorithm. The related articles function has been judged to be so precise that some researchers suggest it can be used instead of a full search, a strong feature of PubMed is its ability to automatically link to MeSH terms and subheadings. Examples would be, bad breath links to halitosis, heart attack to myocardial infarction, where appropriate, these MeSH terms are automatically expanded, that is, include more specific terms. Terms like nursing are automatically linked to Nursing or Nursing and this important feature makes PubMed searches automatically more sensitive and avoids false-negative hits by compensating for the diversity of medical terminology. The My NCBI area can be accessed from any computer with web-access, an earlier version of My NCBI was called PubMed Cubby

25.
Cholesterol
–
Cholesterol, from the Ancient Greek chole- and stereos followed by the chemical suffix -ol for an alcohol, is an organic molecule. Cholesterol enables animal cells to dispense with a wall, thereby allowing animal cells to change shape rapidly. In addition to its importance for cell structure, cholesterol also serves as a precursor for the biosynthesis of steroid hormones, bile acid. Cholesterol is the principal sterol synthesized by all animals, in vertebrates, hepatic cells typically produce the greatest amounts. It is absent among prokaryotes, although there are exceptions, such as Mycoplasma. François Poulletier de la Salle first identified cholesterol in solid form in gallstones in 1769, however, it was not until 1815 that chemist Michel Eugène Chevreul named the compound cholesterine. Furthermore, it can be absorbed directly from animal-based foods, a human male weighing 68 kg normally synthesizes about 1 gram per day, and his body contains about 35 g, mostly contained within the cell membranes. Typical daily cholesterol dietary intake for a man in the United States is 307 mg, most ingested cholesterol is esterified, and esterified cholesterol is poorly absorbed. The body also compensates for any absorption of cholesterol by reducing cholesterol synthesis. For these reasons, cholesterol in food, seven to ten hours after ingestion, has little and it is also important to recognize, however, that the concentrations measured in the samples of blood plasma vary with the measurement methods used. Cholesterol is recycled in the body, the liver excretes it in a non-esterified form into the digestive tract. Typically, about 50% of the excreted cholesterol is reabsorbed by the small intestine back into the bloodstream, plants make cholesterol in very small amounts. Plants manufacture phytosterols, which can compete with cholesterol for reabsorption in the intestinal tract, when intestinal lining cells absorb phytosterols, in place of cholesterol, they usually excrete the phytosterol molecules back into the GI tract, an important protective mechanism. Cholesterol, given that it composes about 30% of all cell membranes, is required to build. The membrane remains stable and durable without being rigid, allowing cells to change shape. In this structural role, cholesterol also reduces the permeability of the membrane to neutral solutes, hydrogen ions. Within the cell membrane, cholesterol also functions in intracellular transport, cell signaling, cholesterol is essential for the structure and function of invaginated caveolae and clathrin-coated pits, including caveola-dependent and clathrin-dependent endocytosis. The role of cholesterol in endocytosis of these types can be investigated by using methyl beta cyclodextrin to remove cholesterol from the plasma membrane, in multiple layers, cholesterol and phospholipids, both electrical insulators, can facilitate speed of transmission of electrical impulses along nerve tissue

26.
Pregnenolone
–
In addition, pregnenolone is biologically active in its own right, acting as a neurosteroid. This conversion involves hydroxylation of the chain at the C20 and C22 positions. To assay conversion of cholesterol to pregnenolone, radiolabelled cholesterol has been used, Pregnenolone product can be separated from cholesterol substrate using Sephadex LH-20 minicolumns. Pregnenolone is produced mainly in the gonads, adrenal glands, Pregnenolone undergoes further steroid metabolism in one of several ways, Pregnenolone can be converted into progesterone. The critical enzyme step is two-fold using a 3β-hydroxysteroid dehydrogenase and a Δ5-4 isomerase, the latter transfers the double bond from C5 to C4 on the A ring. Progesterone is the entry into the Δ4 pathway, resulting in production of 17α-hydroxyprogesterone and androstenedione, aldosterone and corticosteroids are also derived from progesterone or its derivatives. Pregnenolone can be converted to 17α-hydroxypregnenolone by the enzyme 17α-hydroxylase, using this pathway, termed Δ5 pathway, the next step is conversion to dehydroepiandrosterone via 17, 20-lyase. DHEA is the precursor of androstenedione, Pregnenolone can be converted to androstadienol by 16-ene synthase. Pregnenolone can be converted to sulfate by steroid sulfotransferase. Neurosteroids affect synaptic functioning, are neuroprotective, and enhance myelinization, Pregnenolone and its sulfate ester are under investigation for their potential to improve cognitive and memory functioning. Pregnenolone is also being considered as a treatment for schizophrenia. In addition, pregnenolone sulfate has been shown to activate the transient receptor potential M3 ion channel in hepatocytes and pancreatic islets causing calcium entry, Pregnenolone is involved in a natural negative feedback loop against CB1 receptor activation in animals. In contrast to pregnenolone, pregnenolone sulfate did not bind to microtubules, however, progesterone did and with similar affinity to pregnenolone, although unlike pregnenolone, it did not increase binding of MAP2 to tubulin. Pregnenolone was found to induce tubule polymerization in neuronal cultures and to increase growth in PC12 cells treated with nerve growth factor. As such, pregnenolone may control formation and stabilization of microtubules in neurons, Pregnenolone has been found to act as an agonist of the pregnane X receptor. This is in accordance with findings on the conversion of DHEA into testosterone, sripada et al. reported that oral pregnenolone is preferentially metabolized into the neurosteroid allopregnanolone rather than into other steroids such as DHEA or cortisol. Pregnanolone levels increased by approximately 60% while DHEA levels decreased non-significantly by approximately 5%, another study found that allopregnanolone levels were increased by 3-fold at 2 hours post-administration following a single 400 mg oral dose of pregnenolone. In addition to allopregnanolone, exogenous pregnenolone also functions as a prohormone of pregnenolone sulfate, Pregnenolone is lipophilic and readily crosses the blood-brain-barrier

Structures of selected endogenous nuclear receptor ligands and the name of the receptor that each binds to.

Structural Organization of Nuclear Receptors Top – Schematic 1D amino acid sequence of a nuclear receptor. Bottom – 3D structures of the DBD (bound to DNA) and LBD (bound to hormone) regions of the nuclear receptor. The structures shown are of the estrogen receptor. Experimental structures of N-terminal domain (A/B), hinge region (D), and C-terminal domain (F) have not been determined therefore are represented by red, purple, and orange dashed lines, respectively.

Mechanism of class I nuclear receptor action. A class I nuclear receptor (NR), in the absence of ligand, is located in the cytosol. Hormone binding to the NR triggers dissociation of heat shock proteins (HSP), dimerization, and translocation to the nucleus, where the NR binds to a specific sequence of DNA known as a hormone response element (HRE). The nuclear receptor DNA complex in turn recruits other proteins that are responsible for transcription of downstream DNA into mRNA, which is eventually translated into protein, which results in a change in cell function.

Dexamethasone - a synthetic glucocorticoid binds more powerfully to the glucocorticoid receptor than cortisol does. Dexamethasone is based on the cortisol structure but differs at three positions (extra double bond in the A-ring between carbons 1 and 2 and addition of a 9-α-fluoro group and a 16-α-methyl substituent).